Research Interests:

The aim of my PhD was to assess the risk posed by Batrachochytrium dendrobatidis (Bd), to the amphibians of a group of Pyrenean Lakes. To do so, I focussed principally on the common midwife toad (Alytes obstetricans), which, in parts of its range has suffered population declines and even local extinction as a result of exposure to Bd. I took advantage of a well-described spatial system of Bd infection, located in the French Pyrenees. Mass mortalities, due to chytridiomycosis, have been observed in populations of the highly susceptible Alytes obstetricans since the discovery of the pathogen in this area in 2002. I aimed to determine whether infection with chytridiomycosis has the potential to cause declines in this species across the affected region, and whether all populations are equally at risk. I addressed a number of key questions related to this system:

Is there a lethal dose of Bd infection in Alytes obstetricans within this system?

Are populations of infected Alytes obstetricans decreasing over time?

Is there a difference in disease induced mortality rates of infected Alytes obstetricans among populations?

Does the prevalence and intensity of infection in Alytes obstetricans vary over time, and does this affect the infection status of the greater amphibian community?

I examined whether I could infer a threshold of infection based on comparison of swab data taken from infected Alytes obstetricans metamorphs exhibiting different clinical states. These data were further used to ascertain how reliable the current method of Bd detection (swab sampling) is at providing an accurate representation of the true burden of infection suffered by an individual.

I assessed whether populations are declining or not in the presence of infection, by measuring abundance of Alytes obstetricans over-wintered tadpoles over time. This was undertaken by carrying out a number of capture mark recapture studies at three focal sites, using visible implant elastomer (VIE) as a marker of over-wintered tadpoles.

I investigated the nature of host parasite interactions and how they compare amongst three different sites, by quantifying mortality rates over time in a laboratory set-up, then comparing these to estimates of mortality in the field. Additionally, data were collected that would allow investigation of a hosts ability to persist with infection, the existence of infection thresholds, and the temporal variation of infection within individual hosts.

I determined any changes in host- parasite interactions by focusing on one site and investigating the response to Bd over time in three different host species with varying susceptibility. I investigated the changes in prevalence and infection intensity over a seven year period and investigated the potential influence of environmental variation in the changes observed.